| 1. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Concurrent estimation of space and frequency variation for dielectrics: a microwave tomography system for process sensing applications
- 2011
-
Ingår i: Proceedings of the 9th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances, Kansas City, MO USA, May 31 - June 3, 2011. - 9781629934556 ; , s. 177-184
-
Konferensbidrag (refereegranskat)abstract
- In many powder processing operations, the effective complex permittivity of the material under processing yields important information concerning the state of the process. This complex permittivity varies in general with respect to both space and frequency. For an accurate estimation of the process material parameters, it is important to be able to incorporate these dependencies in the estimation algorithm. Here, we present a rather general type of parameterization that is tailored for this type of situation. The parameterization is described in terms of a parameterization mesh, which makes it feasible to refine the computational mesh without influencing the number of degrees of freedom in the estimation problem. A test case demonstrates that our approach can yield accurate reconstructions.
|
|
| 2. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Determination of model order for inverse scattering applications
- 2010
-
Ingår i: Proceedings of the V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010 J. C. F. Pereira, A. Sequeira and J. M. C. Pereira (Eds) Lisbon, Portugal,14-17 June 2010. - 9789899677814
-
Konferensbidrag (refereegranskat)
|
|
| 3. |
- Chung, P. J., et al.
(författare)
-
Broadband ML estimation under model order uncertainty
- 2010
-
Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 90:5, s. 1350-1356
-
Tidskriftsartikel (refereegranskat)abstract
- The number of signals hidden in data plays a crucial role in array processing. When this information is not available, conventional approaches apply information theoretic criteria or multiple hypothesis tests to simultaneously estimate model order and parameter. These methods are usually computationally intensive, since ML estimates are required for a hierarchy of nested models. In this contribution, we propose a computationally efficient solution to avoid this full search procedure and address issues unique to the broadband case. Our max-search approach computes ML estimates only for the maximally hypothesized number of signals, and selects relevant components through hypothesis testing. Furthermore, we introduce a criterion based on the rank of the steering matrix to reduce indistinguishable components caused by overparameterization. Numerical experiments show that despite model order uncertainty, the proposed method achieves comparable estimation and detection accuracy as standard methods, but at much lower computational expense. (C) 2009 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Ferreol, A., et al.
(författare)
-
Statistical Analysis of the MUSIC Algorithm in the Presence of Modeling Errors, Taking Into Account the Resolution Probability
- 2010
-
Ingår i: IEEE Transactions on Signal Processing. - 1941-0476 .- 1053-587X. ; 58:8, s. 4156-4166
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers the statistical performance of the MUSIC method under the condition that two closely spaced sources impinging on an array of sensors are effectively resolved, i.e., the spectrum exhibits two peaks in the neighborhood of the true directions-of-arrival (DOA). The MUSIC algorithm is known to have an infinite resolution power in theory. However, in the presence of modeling errors, sources can not be resolved with certainty, even if the array correlation matrix is perfectly known. The focus of this paper is to predict the bias and variance of the DOA estimates taking into account the possible resolution failure of MUSIC. This performance prediction, based on our recent mathematical investigation, is new to the best of our knowledge. A general mathematical framework to derive closed form expressions of the bias and variance versus the model mismatch, conditioned on a general statistical resolution test is proposed. In order to illustrate our mathematical approach, statistical tests with one and two conditions, respectively, are investigated. The accuracy of the performance prediction is illustrated in a simulation study. It is found that the proposed approach outperforms the "classical" technique, which ignores the possible resolution failure of the MUSIC algorithm. Therefore, our results provide better tools for determining the necessary antenna calibration accuracy to achieve some targeted specifications on the estimator performance.
|
|
| 5. |
- Johansson, Eija, 1982, et al.
(författare)
-
Interpolation based on stationary and adaptive AR(1) modeling
- 2011
-
Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781457705397 ; , s. 4052-4055
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we describe a minimal mean square error (MMSE) optimal interpolation filter for discrete random signals. We explicitly derive the interpolation filter for a first-order autoregressive process (AR(1)), and show that the filter depends only on the two adjacent points. The result is extended by developing an algorithm called local AR approximation (LARA), where a random signal is locally estimated as an AR(1) process. Experimental evaluation illustrates that LARA interpolation yields a lower mean square error than other common interpolation techniques, including linear, spline and local polynomial approximation (LPA).
|
|
| 6. |
- Khademi, Seyran, 1981, et al.
(författare)
-
Peak-to-Average-Power-Ratio (PAPR) reduction in WiMAX and OFDM/A systems
- 2011
-
Ingår i: EURASIP Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1687-6180. ; , s. Article Number: 38-
-
Tidskriftsartikel (refereegranskat)abstract
- A peak to average power ratio (PAPR) reduction method is proposed that exploits the precoding or beamforming mode in WiMAX. The method is applicable to any OFDM/A systems that implements beamforming using dedicated pilots which use the same beamforming antenna weights for both pilots and data. Beamforming performance depends on the relative phase shift between antennas, but is unaffected by a phase shift common to all antennas. PAPR, on the other hand, changes with a common phase shift and this paper exploits that property. An effective optimization technique based on sequential quadratic programming is proposed to compute the common phase shift. The proposed technique has several advantages compared with traditional PAPR reduction techniques in that it does not require any side-information and has no effect on power and bit-error-rate while providing better PAPR reduction performance than most other methods.
|
|
| 7. |
- Li, J., et al.
(författare)
-
Sensor Array and Multichannel Signal Processing
- 2011
-
Ingår i: IEEE Signal Processing Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-0792 .- 1053-5888. ; 28:5, s. 157-158
-
Tidskriftsartikel (refereegranskat)abstract
- This article follows the ICASSP 2011 Trends in Sensor Array and Multichannel Signal Processing (SAM SP) expert session and represents our views on continuing and emergingresearch areas in this field.
|
|
| 8. |
- Lioliou, Panagiota, 1982, et al.
(författare)
-
Bayesian Channel Estimation Techniques for AF MIMO Relaying Systems
- 2011
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424483273 ; , s. Art. no. 6093283-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the fundamental problem of channel estimation in multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying systems operating over random channels. Using the Bayesian framework, linear minimum mean square error (LMMSE) and expectation-maximization (EM) based maximum a posteriori (MAP) channel estimation algorithms are developed, that provide the destination with full knowledge of all channel parameters involved in the transmission. The performance of the proposed algorithms is evaluated in terms of the mean square error (MSE) as a function of the signal-to-noise ratio (SNR) during the training interval. Our simulation results show that the incorporation of prior knowledge into the channel estimation algorithm offers improved performance, especially in the low SNR regime.
|
|
| 9. |
- Lioliou, Panagiota, 1982, et al.
(författare)
-
Self-Interference Suppression in Full-Duplex MIMO Relays
- 2010
-
Ingår i: 44th Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781424497218 ; , s. 658-662
-
Konferensbidrag (refereegranskat)abstract
- Full-duplex relays can provide cost-effective cover-age extension and throughput enhancement. However, the main limiting factor is the resulting self-interference signal which deteriorates the relay performance. In this paper, we propose a novel technique for self-interference suppression in full-duplex Multiple-Input Multiple-Output (MIMO) relays. The relay employs transmit and receive weight filters for suppressing the self-interference signal. Unlike existing techniques that are based on zero forcing of self-interference, we aim at maximizing the ratio between the power of the useful signal to the self-interference power at the relay reception and transmission. Our simulation results show that the proposed algorithm outperforms the existing schemes since it can suppress interference substantially with less impact on the useful signal.
|
|
| 10. |
- Mecklenbräuker, Christoph F., et al.
(författare)
-
Eigenbeam transmission over line-of-sight MIMO channels for fixed microwave links
- 2011
-
Ingår i: Proceedings - ITG/IEEE Workshop on Smart Antennas (WSA). - 9781612840741
-
Konferensbidrag (refereegranskat)abstract
- We propose and analyze eigenbeam transmission over line-of-sight (LOS) multiple-input multiple-output (MIMO) channels with linear reception. In particular, we consider fixed point-to-point microwave links for which the singular value decomposition of the LOS MIMO channel matrix is analytically derived. We demonstrate that the Tx eigenbeams can be defined without channel state information at the transmitter and that the beams admit an insightful physical interpretation. We also evaluate the performance of a lattice-reduction aided linear receiver through numerical simulations.
|
|
